| CNC machine tool is the key equipment to achieve high speed machining,and Motorized spindle is the core component of CNC machine tools,Its dynamic characteristics are important factors affecting the machining accuracy and cutting stability of machine tools.However,in the process of high-speed spindle rotation,the thermal displacement of bearing raceway will be caused by the heat generation of spindle motor and bearing system and change the dynamic performance of the motorized spindle rotor system significantly.Therefore,the coupling analysis of the dynamic and thermal characteristics of the motorized spindle has become an urgent need for the development of the motorized spindle.In this thesis,the 150MD30Y10 motorized spindle is taken as the research object.In order to obtain the influence of the thermal characteristics of the motorized spindle on the dynamic performance of bearing and motorized spindle,the following research work is carried out:Considering the drive system and heat dissipation system,the internal heat source and the heat dissipation conditions of motorized spindle are determined.The finite element model of the motorized spindle temperature field is established by using COMSOL software.The distribution of internal temperature of motorized spindle at different speeds is obtained.The relative axial thermal displacement and relative radial thermal displacement of bearing are calculated according to the temperature obtained by simulation.Considering the thermal displacement of the inner and outer raceway of the bearing,based on the pseudo-static method,the dynamic performance of the bearing is solved.The bearing stiffness under different preload and rolling material element are also compared and analyzed.By using ANSYS workbench finite element analysis software,the finite element model of the motorized spindle rotor system is established.Using the support stiffness of the bearing as the boundary condition,the modal analysis and harmonic response analysis of the motorized spindle system are carried out,and the dynamic characteristics of the centrifugal expansion rotor system based on the thermal displacement of the bearing are obtained.The effects of preload and rolling element material on the dynamic characteristics of the rotor system are investigated.The temperature rise experiment,vibration experiment and modal experiment of the motorized spindle are carried out,respectively.The transient temperature rise,steady temperature rise and the modal of the motorized spindle obtained from the experiment are compared with the simulation results,which verifies the accuracy of the established finite element model.During the operation,the temperature rise of each part of the motorized spindle has a non-linear relationship with time,and its growth rate decreases gradually.After a period of time,a steady-state temperature field will be formed.The temperature distribution inside the motorized spindle is very uneven,and the high temperature appears the bearing and the rotor.Due to the influence of temperature rise,the inner and outer rings of the bearing produces relative thermal displacement,which increases with the increase of rotational speed.When the thermal displacement and centrifugal expansion of the bearing are taken into accounted,the contact loads between the rolling elements and raceways increase,the contact angles decrease and the bearing stiffness increases,which cause the natural frequency of the rotor system increasing with the increase of the rotational speed and the stiffness of the rotor shaft compensated.Through comparative analysis,it can be concluded that using ceramic ball bearings or properly increasing preload can effectively improve bearing stiffness and dynamic characteristics of motorized spindle.The error of temperature field between simulation and experiment is less than 10%,and the error of natural frequency is less than 15%.Therefore,the established model has high accuracy and can be used for parameter studies.In this thesis,the coupled dynamic and thermal characteristics of the motorized spindle are analyzed.The dynamic characteristics of the bearing and the motorized spindle during the working process are obtained,which provides theoretical support for the design and optimization of the motorized spindle. |
PDF Full Text Request